I'd like this folder to be placed directly under the webapp-root.
This isn't going to work. All those files will get lost whenever you redeploy the webapp or even when you restart the server. Those files are namely not contained as part of the original WAR.
You need to store them in a fixed path outside the webapp's context. E.g. /var/webapp/uploads. You can configure this path in a properties file or as a system property.
